Calling File::Glob::bsd_glob with the unsupported flag GLOB_ALTDIRFUNC would cause an access violation / segfault.
A Perl program that accepts a flags value from an external source could expose itself to denial of service or arbitrary code execution attacks.
There are no known exploits in the wild.
The problem has been corrected by explicitly disabling all unsupported flags and setting unused function pointers to null.
Bug reported by Clément Lecigne.

Poorly written perl code that allows an attacker to specify the count to perl's 'x' string repeat operator can already cause a memory exhaustion denial-of-service attack.
A flaw in versions of perl before 5.15.5 can escalate that into a heap buffer overrun; coupled with versions of glibc before 2.16,
it possibly allows the execution of arbitrary code.

($<,$>) = (...) stopped working properly in 5.12.0.
It is supposed to make a single setreuid() call,
rather than calling setruid() and seteuid() separately.
Consequently it did not work properly.
This has been fixed [perl #75212].

Fixed a regression of kill() when a match variable is used for the process ID to kill [perl #75812].

UNIVERSAL::VERSION no longer leaks memory.
It started leaking in Perl 5.10.0.

split() no longer modifies @_ when called in scalar or void context.
In void context it now produces a "Useless use of split" warning.
This is actually a change introduced in perl 5.12.0,
but it was missed from that release's perl5120delta.

The list above is almost certainly incomplete as it is automatically generated from version control history.
In particular,
it does not include the names of the (very much appreciated) contributors who reported issues to the Perl bug tracker.

Many of the changes included in this version originated in the CPAN modules included in Perl's core.
We're grateful to the entire CPAN community for helping Perl to flourish.

For a more complete list of all of Perl's historical contributors,
please see the AUTHORS file in the Perl source distribution.

If you find what you think is a bug,
you might check the articles recently posted to the comp.lang.perl.misc newsgroup and the perl bug database at http://rt.perl.org/perlbug/ .
There may also be information at http://www.perl.org/ ,
the Perl Home Page.

If you believe you have an unreported bug,
please run the perlbug program included with your release.
Be sure to trim your bug down to a tiny but sufficient test case.
Your bug report,
along with the output of perl -V,
will be sent off to perlbug@perl.org to be analysed by the Perl porting team.

If the bug you are reporting has security implications,
which make it inappropriate to send to a publicly archived mailing list,
then please send it to perl5-security-report@perl.org.
This points to a closed subscription unarchived mailing list,
which includes all the core committers,
who be able to help assess the impact of issues,
figure out a resolution,
and help co-ordinate the release of patches to mitigate or fix the problem across all platforms on which Perl is supported.
Please only use this address for security issues in the Perl core,
not for modules independently distributed on CPAN.